/*=====================================================================*
 *                   Copyright (C) 2011 Paul Mineiro                   *
 * All rights reserved.                                                *
 *                                                                     *
 * Redistribution and use in source and binary forms, with             *
 * or without modification, are permitted provided that the            *
 * following conditions are met:                                       *
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 *     * Redistributions of source code must retain the                *
 *     above copyright notice, this list of conditions and             *
 *     the following disclaimer.                                       *
 *                                                                     *
 *     * Redistributions in binary form must reproduce the             *
 *     above copyright notice, this list of conditions and             *
 *     the following disclaimer in the documentation and/or            *
 *     other materials provided with the distribution.                 *
 *                                                                     *
 *     * Neither the name of Paul Mineiro nor the names                *
 *     of other contributors may be used to endorse or promote         *
 *     products derived from this software without specific            *
 *     prior written permission.                                       *
 *                                                                     *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND              *
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,         *
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES               *
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE             *
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER               *
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,                 *
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES            *
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE           *
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 *                                                                     *
 * Contact: Paul Mineiro <paul@mineiro.com>                            *
 *=====================================================================*/

#include "learningrate.hh"

#include <boost/optional.hpp>
#include <boost/none.hpp>
#include <map>
#include <stdexcept>

namespace
{
  std::map<std::string, flassol::LearningRateFactory>&
  get_registry ()
    {
      static std::map<std::string, flassol::LearningRateFactory> f;

      return f;
    }

  boost::optional<float>
  maybe_parse_float (const std::string& s)
    {
      float rv;
      char* endptr;

      rv = strtof (s.c_str (), &endptr);

      if (s.c_str ()[0] != '\0' && *endptr == '\0')
        {
          return rv;
        }

      return boost::none;
    }
}

namespace flassol
{

LearningRateFactory
register_learning_rate_factory (const std::string&  s,
                                LearningRateFactory l)
  {
    std::map<std::string, LearningRateFactory>& f = get_registry ();

    f[s] = l;

    return l;
  }

std::auto_ptr<LearningRate>
get_learning_rate (const std::string& s)
  {
    std::map<std::string, LearningRateFactory>& f = get_registry ();
    std::string::size_type pos = s.find_first_of (" (", 0);
    std::string name = (pos == std::string::npos) ? s : s.substr (0, pos);
    std::map<std::string, LearningRateFactory>::iterator i = f.find (name);

    if (i == f.end ())
      {
        // possibly just a floating point number was entered.
        // treat this as powerlaw(float)

        boost::optional<float> number = maybe_parse_float (s);

        if (number)
          {
            i = f.find ("powerlaw");

            if (i != f.end ())
              {
                return std::auto_ptr<LearningRate> ((*i->second) (s));
              }
          }

        throw std::invalid_argument ("unknown learning rate function");
      }
    else
      {
        return std::auto_ptr<LearningRate> ((*i->second) (s));
      }
  }

std::string
get_registered_learning_rates ()
  {
    std::string rv;
    std::map<std::string, LearningRateFactory>& f = get_registry ();

    for (std::map<std::string, LearningRateFactory>::const_iterator x = f.begin ();
         x != f.end ();
         ++x)
      {
        rv += x->first;
        rv += " ";
      }

    return rv;
  }

};
